Neuropath 3

Question 1

What is TSE and what are the characteristics of it?

Answer 1

• Transmissible spongiform encephalopathy (TSE)
• Neurodegenerative diseases
• Rapidly progressive, always fatal
• Affect humans and animals
• Long incubation periods e.g. in PNG it took 45 years to develop disease
• Prion-only hypothesis widely accepted

Question 2

Why is it refered to as spongiform changes?

Answer 2

These uniform changes are unique to prion disease and the appearance under the microscope is similar to the appearance of a sponge.

Question 3

Is neuronal degeneration/loss/death the same as spongiform changes?

Answer 3

No, neuronal degeneration can be mirrowed with spongiform changes but are quite different. With neuronal loss we will see spaces (vacuolation)

Question 4

Name the TSE diseases and which part of the brain we will see initial changes.

Answer 4

• Brain stem: scraple, BSE and chronic wasting disease
• Cerebellum: kuru
• Thalamus: fatal familial insomnia
• Cerebral cortex: classic CJD

Question 5

Name the important human TSEs

Answer 5

• Kuru
• Creutzefeldt-Jakob disease (CJD) - associated with cannabilism in PNG
• Variant Creutzefeldt-Jakob disease (vCJD) - associated with made cow disease
• Gerstmann-Sträussler Scheinker Syndrome (GSS)

Question 6

Name the main animal TSEs

Answer 6

• Scrapie
• Bovine Spongiform Encephalopathy (BSE)
• Chronic Wasting Disease (CWD)

Question 7

What is the link between scrapies and humans?

Answer 7

• Sheep scrapies doesn’t affect humans but is transmissible to cows to cause BSE which can be transmitted to humans as CJD

Question 8

Is culling an efficient way to manage scrapie?

Answer 8

No, the prion protein can lay dormant in soil for years, resulting in outbreaks years after infected individuals have been removed from the herd

Question 9

Is/has scrapie been in Australia?

Answer 9

Yes, we are aware of 5 cases in VIC (atypical scrapie)

Question 10

How do sheep get scrapie?

Answer 10

Ingestion of contaminated material (can stay in the environment for up to 15 years).
Dissemination of prions:
- Systemic
- lymphatic
- nervous system (most effective route)

Question 11

Is Bovine spongiform encephalopathy (BSE) a big issue?

Answer 11

No, not anymore.

Question 12

What are the possible causes of BSE?

Answer 12

 The practice of feeding cattle rendered animal parts was implicated
 Rendered material was from either:
* Scrapie infected sheep
* Cattle with spontaneous BSE

Question 13

What clinical symptoms are assoicated with Chronic wasting disease (CWD)?

Answer 13

 Weight loss
 Behavioural changes
 Excessive salivation
 Difficulty swallowing

Question 13

What clinical symptoms are assoicated with Chronic wasting disease (CWD)?

Answer 13

 Weight loss
 Behavioural changes
 Excessive salivation
 Difficulty swallowing

Question 14

What is the main issue with CWD?

Answer 14

Wildlife resovoirs -> difficult to control

Question 15

What is a prion?

Answer 15

• Shortened form of Proteinaceous infectious particles
• Prions are single molecules containing about 250 amino acids
• They are abnormal variants of proteins which normally occur in cells
• Prions have the ability to convert the normal forms that they come into contact with into abnormal forms

Question 16

List some features of prions

Answer 16

• Prions are non immunogens and do not induce an immune response
• Prions are not easy to decompose biologically
• They are resistant to high temperatures & disinfectants
• Prions are resistant to digestion by proteases

Question 17

Explain the prion hypothesis

Answer 17

• PrP is a normal cellular protein referred to as PrPc
• Diseased brain contains aberrant PrP which is referred to as PrPSc
• PrPSc has the ability to convert PrPc to itself
• A chain reaction follows, resulting in a cluster of tangled, nonfunctional proteins called plaques, which are aggregates of PrPSc in the brain
• PrPSc requires normal protein (PrPc) to produce more abnormal protein

Question 18

If you inoculate strain A into species A what will happen? Compare this to injecting strain B into species A.

Answer 18

• If you inoculate strain A into species A – will keep getting same disease profile
• If you inject strain B into species A – will get similar disease profile

Question 19

Explain the species barrier phenomenon.

Answer 19

If you inject prions from species B to a different species = shorten incubation period

Question 20

Does prion disease affect all species?

Answer 20

Dogs (besides rottweilers) and rabbits are not affected by prion disease.